尿素对燃煤电厂水冷壁管15CrMo钢腐蚀特性研究

doi:10.11902/1005.4537.2018.067

中国腐蚀与防护学报

2019, Vol. 39

Issue (2): 114-122 DOI: 10.11902/1005.4537.2018.067

研究报告

本期目录 | 过刊浏览

尿素对燃煤电厂水冷壁管15CrMo钢腐蚀特性研究

田龙标¹,朱志平¹(

),张春雷²,喻强¹,杨磊¹

1. 长沙理工大学化学与生物工程学院长沙 410114
2. 大唐华中电力试验研究院郑州 450001

Urea Induced Corrosion of 15CrMo Steel for Water Cooled Wall Tubes in Coal-fired Power Plants

Longbiao TIAN¹,Zhiping ZHU¹(

),Chunlei ZHANG²,Qiang YU¹,Lei YANG¹

1. School of Chemical and Biological Engineering, Changsha University of Science and Technology, Changsha 410014, China
2. Datang Central-China Electric Power Test Research Institute, Zhengzhou 450001, China

全文: PDF(8950 KB) HTML

摘要:

针对某燃煤电厂水冷壁管出现的尿素腐蚀问题，在高压釜中模拟电厂现场运行工况，研究了尿素在高温条件下对水冷壁管15CrMo钢的腐蚀特性。在270 ℃、5个尿素浓度 (70，140，280，560和840 mg/L) 下进行了高温分解实验与挂片实验，同时进行了典型浓度280 mg/L、270 ℃条件下定时分解实验，测定了实验中汽、液样品的TOC值与红外吸收光谱，用电化学方法与微观表征技术 (SEM，EDS和XRD) 研究了尿素分解残液对15CrMo钢的腐蚀特性。结果表明：尿素在分解过程中会产生腐蚀性离子NH₂COO^-而对水冷壁管产生腐蚀，且15CrMo钢的腐蚀速率随尿素浓度的增大而加快，最大腐蚀速率达0.593 mm/a。消除脱硝系统的局部设计缺陷可以有效防止尿素对水冷壁管的腐蚀。

关键词 ：尿素, 水冷壁管, 15CrMo, 氨基甲酸铵, 腐蚀

Abstract：

In order to figure out the corrosion problem of water cooled-wall tubes caused by urea in a coal-fired power plant, the corrosion behavior of 15CrMo steel at high temperature were studied in urea containing media with an autoclave aiming to simulate the operation situation of the power plant. The urea decomposition process and the corrosion of the steel were simultaneously examined at 270 ℃ in solutions with varying urea concentrations of 70, 140, 280, 560 and 840 mg/L, respectively. Peculiarly, during the decomposition process of the medium with urea concentration of 280 mg/L, the yield liquid- and vapor-phase were extracted from the reaction chamber at different time intervals for characterization with TOC analyzer and infrared spectrometer. Besides, the corrosion of 15CrMo steel in the yield urea solution were assessed by weight loss measurement, electrochemical impedance spectroscopy and polarization curve measurement. The surface morphology of the tested steel was characterized by SEM, EDS and XRD. Results show that urea produced corrosive ions NH₂COO^- during decomposition, which caused the corrosion of water wall tubes. The corrosion rate of 15CrMo steel increased with the increasing urea concentration, and the maximum corrosion rate was 0.593 mm/a. The urea leaked into water cooled wall tubes may be ascribed to certain consequences of improper design of the denitrification system, therefore, to eliminate such engineering errors can effectively prevent the occurrence of urea induced corrosion for water-cooled wall tubes.

Key words： urea water wall tube 15CrMo ammonium carbamate corrosion

收稿日期: 2018-05-18

ZTFLH:

TG172.2

基金资助:湖南省科技计划重点项目(2013GK2016)

通讯作者: 朱志平 E-mail: zzp8389@163.com

Corresponding author: Zhiping ZHU E-mail: zzp8389@163.com

作者简介: 田龙标，男，1993年生，硕士生

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引用本文:

田龙标,朱志平,张春雷,喻强,杨磊. 尿素对燃煤电厂水冷壁管15CrMo钢腐蚀特性研究[J]. 中国腐蚀与防护学报, 2019, 39(2): 114-122.
Longbiao TIAN, Zhiping ZHU, Chunlei ZHANG, Qiang YU, Lei YANG. Urea Induced Corrosion of 15CrMo Steel for Water Cooled Wall Tubes in Coal-fired Power Plants. Journal of Chinese Society for Corrosion and protection, 2019, 39(2): 114-122.

链接本文:

https://www.jcscp.org/CN/10.11902/1005.4537.2018.067 或 https://www.jcscp.org/CN/Y2019/V39/I2/114

图1 尿素高温分解实验装置

图2 尿素分解8 h后汽、液相TOC含量随初始浓度的变化

图3 280 mg/L尿素分解不同时间后的汽、液相TOC含量随时间的变化

图4 尿素溶液分解前后红外谱图

图5 15CrMo钢在尿素分解残液中的极化曲线

图6 15CrMo钢在尿素溶液中的极化曲线

表1 15CrMo钢在尿素分解残液中的极化曲线参数

表2 15CrMo钢在尿素溶液中的极化曲线参数

图7 15CrMo钢在尿素分解残液中的电化学阻抗Nyquist图

图8 15CrMo钢在尿素分解残液中阻抗谱的等效电路

表3 15CrMo钢在尿素分解残液中的阻抗拟合参数

图9 15CrMo钢腐蚀速率与尿素初始浓度的关系

图10 15CrMo钢试片在尿素溶液中腐蚀前后表面金相图

图11 15CrMo钢在70 mg/L尿素溶液中高温腐蚀后的SEM像与EDS结果

图13 15CrMo钢在140 mg/L尿素溶液中高温腐蚀8 h后的XRD谱

图12 15CrMo钢在140 mg/L尿素溶液中高温腐蚀后的SEM像与EDS结果

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